The invention relates to an assembly comprising a frame element of a motor vehicle and a connecting element, which is provided for attaching a component, and to a method for securing the connecting element to the frame element.
In the production of motor vehicles in the automotive industry, various parts of the motor vehicle are made from appropriate frame structures. Such frame structures include, for example, the chassis of most motor vehicles.
FIG. 5 shows part of a chassis provided for a motor vehicle, or of an appropriate frame structure. The frame structure has formed on it an attachment location ST1, which has two parallel attachment portions, each with a through-opening. A control arm of a wheel-suspension is secured at the attachment location ST1 via a screw connection running through the through-openings.
The frame structure shown in FIG. 5 is a metal structure made from individual frame elements ST2, ST3, etc. The attachment location ST1 is secured to the frame element ST2, for example, by a weld connection. While the vehicle is in operation, forces are introduced via the attachment location ST2 into the frame structure shown in FIG. 5.
Nowadays, for reasons relating to saving weight in the automotive industry, there is a tendency for such frame structures, in particular also in the chassis region, to be produced from fiber-reinforced plastics. In the case of such frame structures produced from fiber-reinforced plastics, the attachment locations are secured to the appropriate frame element by either adhesive-bonding connections and/or screw connections.
For the screw connections, it is necessary to provide appropriate through-openings in the frame element formed from a fiber-reinforced plastic, this resulting in the severing of fibers and thus in the fiber-reinforced plastic being weakened. The corresponding regions of the frame element therefore have to be designed using stronger/thicker materials or have to be reinforced by additional elements.
In the case of the alternative option of securing the attachment location via an adhesive, in contrast, it is necessary to provide large surface areas connected via the adhesive, so that the adhesive-bonding connection does not rupture under the action of intended forces.
Against this background, it is an object of the invention to provide an attachment location or an assembly comprising a frame element of a motor vehicle and a connecting element, provided for attaching a component, which has good stability properties and can be designed straightforwardly.
This object is achieved by an assembly and a method according to embodiments of the invention.
According to the present invention, an assembly comprising a frame element of a motor vehicle, for example a frame element of a chassis of a motor vehicle, and a connecting element, which is provided for attaching a component, for example a control arm belonging to a wheel-suspension, is designed in that the connecting element is secured to the frame element by a fiber winding.
The design of the fiber winding means that there is no need to provide through-passages for screw connections in the frame element, for which reason it is therefore also the case that there is no material weakening of the frame element.
In dependence on the intended force applied to the connecting element, or on the intended force to be introduced into the frame element, and the resulting flow of forces, the fiber winding may be formed in that a fiber is wound around the frame element and the connecting element such that appropriate portions of the fiber run parallel to one another or in a crossed state in the direction of the resulting flow of forces.
It is therefore possible to create, for different force flowpaths, fiber windings which ensure good securing of the connecting element to the frame element and thus a good introduction of forces.
The material of the fiber forming the fiber winding may be, for example, a carbon fiber, a glass fiber, an aramid fiber, a ceramic fiber, a boron fiber, a basalt fiber or a steel fiber.
The fiber winding or the corresponding fiber may be embedded in a matrix. This matrix may be, for example, a duroplast or a thermoplastic. Examples of duroplasts are epoxy resin, unsaturated polyester resin, vinylester resin, phenol formaldehyde resin, diallyl phthalate resin, methacrylate resin, polyurethane, amino resins, melamine resin, urea resin. Examples of thermoplastics are acrylonitrile butadiene styrene, polyamides, polylactate, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyether ether ketone, polyvinyl chloride, polyphenylene sulfide, polysulfone, polyetherimide and polytetrafluoroethylene.
The fiber winding may be formed from an individual fiber of a certain length or from a plurality of such individual fibers. This means that, for example, one fiber is wound in one direction around the connecting element and the frame element and a further fiber is wound in the same direction or in a different direction, once again, around the connecting element and the frame element. The various fibers forming the fiber winding may be formed from the same or different materials mentioned above.
The connecting element is intended to attach a component, for example a control arm of a wheel-suspension system, to the frame element. For this purpose, the connecting element may have, for example, through-openings for a screw connection.
The material of the connecting element may be a fiber-reinforced plastic in which a reinforcing fiber or reinforcing fibers is or are embedded in a matrix made of a duroplast or a thermoplastic. In respect of examples of suitable duroplasts and thermoplastics, reference is made to the duroplasts and thermoplastics already mentioned. The embedded reinforcing fiber(s) may be of different lengths, i.e. short, long or endless. Short fibers have a length ranging from 0.1 to 1 mm, long fibers have a length ranging from 1 to 50 mm and endless fibers have a length>50 mm.
Should the connecting element be formed from metal, it is preferably a milled, cast or welded structure.
In particular, preferably at least edges along which the fiber winding runs are rounded and/or deburred, so that there is no risk of the fiber being damaged.
The frame element may be formed from a metal or a plastic, for example from a fiber-reinforced plastic.
In a preferred configuration of the assembly according to the invention, the frame element extends in a longitudinal direction, the connecting element has an attachment portion, which extends transversely to the longitudinal direction and is intended for attaching the component, and the fiber winding is configured such that it runs around the attachment portion.
In general, the fiber winding may be produced such that the fiber forming the fiber winding runs perpendicularly to the longitudinal direction. If the fiber winding is made from a plurality of individual fibers, it is also possible for the individual fibers to cross over one another. This means that the fiber(s) can form geodetic lines which connect points which, as seen in relation to the longitudinal direction, are located at the same level or are offset in relation to one another.
This configuration is advantageous in particular when tensile and compressive forces occur in the direction transverse to the longitudinal direction, in which the attachment portion extends, said forces being introduced via the attachment portion or the connecting element into the frame element.
In a preferred configuration of the assembly according to the invention, the connecting element has an outer surface, on which the fiber winding runs, wherein the connecting element is configured such that the outer surface of the connecting element is flush with an outer surface of the frame element.
In general, the connecting element and the frame element are adapted to one another such that there is a form fit between them. This ensures that, when an intended force is applied to the connecting element or when an intended force is introduced into the frame element, the connecting element does not rotate in relation to the frame element.
It is possible, for example, for the frame element to have a cross section which runs transversely to the longitudinal direction and is circular-arc-shaped, on the one hand, and linear, on the other hand. This means that, in this region, the frame element has, on the one hand, a planar surface-area portion and also an adjoining circular-arc-shaped surface-area portion. The connecting element is brought into abutment, in particular against the planar surface-area portion of the frame element, such that the outer surface of the connecting element, on which the fiber winding runs, is flush with the circular-arc-shaped portion of the frame element. As a result, there is a continuous transition between the outer surface of the connecting element and the outer surface of the frame element, and the fiber winding therefore does not run over any angular-edge transitions between the connecting element and the frame element.
Furthermore, the connecting element is preferably configured such that it has rounded or deburred edges, so that damage to the fiber winding by the edges of the connecting element is avoided.
In a preferred configuration of the assembly according to the invention, the attachment portion is formed from a first sub-element and a second sub-element, which are assembled so as to enclose the frame element between them. The fiber winding runs around the first and the second sub-elements.
The first sub-element and the second sub-element are preferably configured such that, in the assembled state, they form a joint continuous outer surface. This configuration ensures that the fiber of the fiber winding has a rectilinear progression and does not butt against any sharp edges. In addition, the appropriate edges of the first and second sub-elements may be rounded, so that damage to the fiber winding in the region in which the first and the second sub-elements are assembled is avoided.
In a preferred configuration of the assembly according to the invention, the frame element extends in a longitudinal direction, wherein the connecting element has a bearing portion, which is adapted to an outer surface of the frame element and from which an attachment portion, for attaching the component, extends transversely to the longitudinal direction. The fiber winding is preferably configured such that it runs around the bearing portion and/or the attachment portion. This preferred configuration allows the assembly according to the invention to be adapted to good effect to different requirements relating to force absorption and introduction of forces into the frame element.
If, for example, the attachment portion, running transversely to the longitudinal direction, is provided for attaching a control arm of a wheel-suspension system, it is possible for a fiber winding running around the bearing portion to absorb to better effect, and introduce into the frame element, forces which act in the longitudinal direction.
In a further preferred configuration of the assembly according to the invention, the attachment portion extends from a longitudinally directed end portion of the bearing portion. In this case, the fiber winding may be configured such that it runs around the bearing portion and/or the attachment portion.
In a further preferred configuration of the assembly according to the invention, the bearing portion is formed from a first sub-element and a second sub-element, which are assembled so as to enclose the frame element between them. In this case, the fiber winding is configured such that it runs around the first and second sub-elements of the bearing portion and/or the attachment portion.
This two-part configuration of the bearing portion ensures that the fiber forming the fiber winding has a continuous progression and does not butt against any possible sharp edges. The edges over which the fiber winding has to run may be additionally rounded/deburred.
In a further preferred configuration of the assembly according to the invention, the connecting element includes at least two attachment portions. The attachment portions here may be two separate, independent parts, preferably each extending from a bearing portion, or may be designed in the form of a single part, for example by the two attachment portions extending from a joint bearing portion.
In this case, the fiber winding can run over the bearing portion and/or over the attachment portions.
As already explained, the fiber winding may be produced such that the fiber forming the fiber winding runs perpendicularly to the longitudinal direction. If the fiber winding is made from a plurality of individual fibers, it is also possible for the individual fibers to cross over one another. This means that the fiber(s) can form geodetic lines which connect points which, as seen in relation to the longitudinal direction, are located at the same level or are offset in relation to one another.
The frame element and the connecting element are preferably formed from a fiber-reinforced plastic, the fiber winding being a fiber winding formed from a plastic fiber.
This material-specific configuration of the appropriate elements of the assembly according to the invention means that no corrosion occurs and, furthermore, the frame element, the connecting element and the fiber winding may be configured such that they have the same, or similar, coefficients of thermal expansion.
In a further preferred configuration of the assembly according to the invention, in a region on which the fiber winding runs, the connecting element has a concave surface on which to position the fiber winding.
This concave surface may be constituted, for example, by grooves in which to position the fiber making up the fiber winding. This configuration ensures that slipping of the fiber winding or of individual fiber portions is prevented.
The fiber winding of the assembly according to the invention may be formed from an individual winding or from a plurality of spatially separate sub-windings. It is possible here for the winding or each sub-winding to have a certain number of windings, wherein the number of windings is to be understood to mean how often the fiber(s) forming the winding/sub-winding have been wound around the frame element and the connecting element.
It should again be mentioned here that the fiber winding may be produced such that the fiber forming the winding/sub-winding runs perpendicularly to the longitudinal direction. If the winding/sub-winding is made from a plurality of individual fibers, it is also possible for the individual fibers to cross over one another. This means that the fiber(s) can form geodetic lines which connect points which, as seen in relation to the longitudinal direction, are located at the same level or are offset in relation to one another.
In a further preferred configuration of the assembly according to the invention, in addition to the fiber winding, an integral material bond is formed between the frame element and the connecting element.
Such an integral material bond may be established, for example, via an adhesive. The combination of the fiber winding and the integral material bond means that the assembly according to the invention can be formed to good effect to different requirements relating to introduction of forces into the frame structure. For example, the integral material bond, via the adhesive, absorbs shear stress and the connection produced via the fiber winding absorbs tensile stress.
In a further preferred configuration of the assembly according to the invention, the integral material bond is formed by an adhesive between the frame element and the bearing portion and, at at least one end portion located in the longitudinal direction of the frame element, the bearing portion is designed such that a quantity of adhesive increases.
In other words, the bearing portion is designed such that, at the at least one end portion located in the longitudinal direction of the frame element, it is beveled or stepped so as to increase the gap, between the frame element and bearing portion, in which the adhesive is located. This preferred configuration gives rise to a weakening/reduction in peak stressing, in particular peak stressing resulting from notch effects, occurring at the end portion.
The adhesive may be constituted, for example, by cold- or hot-setting adhesives, soft elastomers or hard adhesives. The gap located between the frame element and the bearing portion may have an order of magnitude of up to 3 mm.
It is also preferable for a projecting bead consisting of adhesive to be formed at the at least one longitudinally directed end portion. This likewise results in the reduction of peak stressing.
The present invention likewise provides a method by which a connecting element provided for attaching a component is secured to a frame element of a motor vehicle. The method includes providing the frame element and the connecting element, wherein the connecting element is secured to the frame element via a fiber winding.
The fiber winding is preferably formed such that, in dependence on the action of intended forces, it runs in the direction of the flow of forces.
The fiber winding can be formed by virtue of a single fiber or a plurality of fibers being wound. The fiber here is wound such that fiber portions run parallel or in a crossed state. In general, the fiber is preferably wound in the direction of the flow of forces.
The fiber winding may have a matrix which is formed from a matrix material and in which the corresponding fiber forming the fiber winding is embedded. The matrix can be produced in that, in a state in which it is impregnated in the matrix material, the fiber forming the fiber winding is wound to secure the connecting element to the frame element, or else the matrix material is applied to the fiber winding following completion of the winding operation.
In a preferred configuration of the method according to the invention, the frame element extends in a longitudinal direction, and the connecting element has an attachment portion, which is intended for attaching the component. Following the securing operation, the attachment portion extends, as intended, transversely to the longitudinal direction, and is provided, for example, for attaching a control arm of a wheel-suspension. The connecting element is secured to the frame element by the fiber winding, a fiber being wound around the attachment portion.
In a further preferred configuration of the method according to the invention, the frame element extends in a longitudinal direction, and the connecting element has a bearing portion, which is adapted to an outer surface of the frame element and from which an attachment portion, for attaching the component, extends transversely to the longitudinal direction. The connecting element is secured to the frame element by the fiber winding, a fiber being wound around the bearing portion and/or the attachment portion.
In general, the fiber winding may be produced such that the fiber forming the fiber winding runs perpendicularly to the longitudinal direction. If the fiber winding is made from a plurality of individual fibers, it is also possible for the individual fibers to cross over one another. This means that the fiber(s) can form geodetic lines which connect points which, as seen in relation to the longitudinal direction, are located at the same level or are offset in relation to one another.
In a further preferred configuration of the method according to the invention, the fiber, for securing the connecting element to the frame element, is wound such that portions of the fiber run parallel to one another or cross over one another.
In a further preferred configuration of the method according to the invention, the fiber is wound in a direction other than a direction in which the attachment portion extends.
In a further preferred configuration of the method according to the invention, the frame element is designed such that it extends in a longitudinal direction and has an abutment surface, on which the connecting element is brought into abutment with a bearing surface, which corresponds to the abutment surface, an integral material bond is established between the abutment surface and the bearing surface, and the fiber winding is formed such that it compresses the integral material bond.
In a further preferred configuration of the method according to the invention, the integral material bond is formed by an adhesive between the abutment surface and the bearing surface such that there is an increase in the quantity of adhesive at at least one longitudinally directed end portion of the connecting element.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.